Material reducing system having oxygen deficient atmosphere

ABSTRACT

A material reducing mill, crusher, or grinder system having means connected thereto to establish an oxygen deficient atmosphere that approaches a zero condition by extracting moisture from the system to enhance the production of a useful product at a temperature below that at which spontaneous combustion might be initiated.

United States Patent Inventor Appl. No. Filed Patented MATERIAL REDUCING SYSTEM HAVING OXYGEN DEFICIENT ATMOSPHERE 6Clatms, 1 Drawing Fig.

U.S.Cl 110/106, 1 241/47- lnt. Cl F23k1/04 Field otSearch 110/106; 241/47, 65

U g \-l llllll lln Primary Examiner-Kenneth W. Sprague Attorney-Gravely, Lieder and Woodruff ABSTRACT: A material reducing mill, crusher, or grinder system having means connected thereto to establish an oxygen deficient atmosphere that approaches a zero condition by extracting moisture from the system to enhance the production of a useful product at a temperature below that at which spontaneous combustion might be initiated.

I MATERIAL REDUCING SYSTEM HAVING OXYGEN DEFICIENT-ATMOSPHERE BRIEF DESCRIPTION OF THE INVENTION This invention relates to improvements in a system that will allow the operation of grinding or material classifying systems under conditions of low oxygen content in the internal atmosphere and at temperatures where the product to be produced will issue below the spontaneous combustion temperature of such product. I

While pollution of the ambient atmosphere in industrial plants and mills is important, it is also extremely important that commercial products should be processed in such a way that explosions, fire hazards, and hazards to operating personnel are adequately protected against. This is especially important in commercial processing apparatus where the product is a combustible such as coal. Coal is a very good example to illustrate the novel and important aspects of the present invention.

A great many industrial operations utilize coal in a finely divided or pulverulent state so that it may be blown into a furnace or other combustion space in a fluent stream. Coal in its fairly large lump size as it is brought from the mines is not suitable for this purpose and consequently must be reduced to a much finer condition so that it will form a fluent stream. One such apparatus for reducing coal to a finely divided state in an atmosphere that will inhibit explosion and fire is disclosed in the U.S. Pat. No. 3,477,650, of Williams granted Nov. 11, 1969. In that patent the system includes a pulverizer mill, and the product is delivered to a suitable cyclone separator where the finely divided product is collected and delivered through a discharge. In order to operate the reducing mill at a sage condition, the system of that patent involves reducing the coal in an oxygen deficient atmosphere and 'at a suitable elevated temperature to control the moisture level of the system as it is changed by the raw product after it enters the mill.

In accomplishing the foregoing aims the present system incorporates a furnace which produces a hot gas having an oxygen deficient characteristic approaching zero oxygen, which gas is then circulated through the system at such a temperature that it has a great ability to pick up moisture and carry it through the system as a vapor. The temperature is maintained at a level high enough so that the internal atmosphere will not reach complete saturation or the dew point.

The principal object of the present invention is to provide means for rendering the system heretofore described completely operable under oxygen deficient conditions and at temperatures below the spontaneous combustion temperature levels of the product being so processed.

A preferred embodiment of the present invention includes a system for directing the oxygen deficient internal circulating gases in the apparatus through a device which will extract the moisture therefrom and obtain the return of the already oxygen deficient gases to the system by way of the furnace so that only a minimum of ambient primary air needs to be admitted for the purpose of operating the furnace at a level where substantially complete or perfect combustion occurs to use up the oxygen as completely as possible and thereby release oxygen deficient hot combustion gases into the system to maintain the desired inert internal atmosphere.

A preferred embodiment of the present invention is shown in the. accompanying schematic diagram of apparatus for extracting moisture from the inert atmosphere in material reducing systems.

DESCRIPTION OF THE APPARATUS The preferred apparatus, diagrammatically shown in the accompanying drawing, is seen to include a pulverizer mill to which hopper 11 is connected by a suitable chute 12 which feeds the raw product through a suitable air lock 13 so as to restrict-the amount of ambient air that is carried into the system with the raw product whichmay be coal. The pulverized coal is carried through a discharge conduit 14 to the upper end of a cyclone separator 15. The pulverized solid material is discharged through the outlet 16 from the bottom of the separator, while the inert gases and fines suspended in the gases are discharged through the conduit 17 from the top of the separator. The separation of the gases and fines that float in the gases from the pulverulent material is facilitated by a suitable blower 18 which sucks the gases and fines from the cyclone separator 15 through the conduit 17 and delivers a portion thereof through the conduit 19 back to the mill It). A portion of the gas flow established by the blower I8 is diverted through conduit 20 to a second separator 21 where the very fine particles that may have remained in suspension are separated and discharged at the outlet 22. The inert gas, after being separated from the fines passes through the conduit 23 to a blower 24.

A furnace 25 is equipped with a primary air blower 26 to supply combustion air and a conduit 27 supplies the gas or the fuel to be consumed in the furnace. It is desirable that combustion be as nearly perfect as possible so that the hot gases discharged from the furnace through the conduit 28 can be as nearly oxygen deficient as is possible, but at least sufficiently oxygen deficient to establish an atmosphere in the system that will be able to pick up moisture to be carried out of the system, and nonresponsive to explosion and combustion conditions. The hot gases in conduit 28 are conducted into the base of the mill 10 and mixed with the recirculated gases supplied through conduit 19.

What has thus far been described briefly is the system disclosed in said Williams U.S. Pat. No. 3,477,650, wherein a portion of the discharge from the blower 24 is normally recirculated through conduit 29 to the furnace 25 and a portion is conducted to atmosphere through a conduit 30. To make up air to replace that which is exhausted through conduit 30, in the'system of said patent, fresh air is supplied through a fresh air conduit 31. However, in the presently preferred embodiment of this invention the exhaust conduit 30 is provided with a bypass conduit 32 which connects into the former fresh air makeup inlet conduit 31, and a spray dehumidifier or scrubber device 33 of known construction for cooling gases to precipitate the moisture is connected into the bypass conduit 32. The device 33 is provided with an outlet conduit 34 for draining off the liquid which is extracted from the gaseous medium moving through the bypass conduit 32.

In order to facilitate the flow of gaseous medium through the bypass conduit 32 the exhaust conduit 30 is provided with a control damper 35 which can be adjusted to force some or all of the flow in conduit 30 to enter the bypass 32 or the conduit 29, or both, whereby these two flows will combine and enter the furnace 25 to be again returned with the hot gases of the combustion process. The proportion of flow in conduit 29 and in the bypass 32 may be regulated by the damper 29A in conduit 29. Closing damper 29A will cause all of the flow through the device 33, whereby the system will function as if the conduit 29 were not present.

Instead of allowing the inert atmosphere or gas in the system to exhaust to atmosphere from conduit 30 at valve 35, it is sometimes useful to pass the flow through the device 33 and then allow the dry inert gas to exit from the system. When operated in this fashion, the valve 35 is closed and the exhausted dry medium is collected for other uses. Accordingly, the conduit 31 downstream of the device 33 may have the exhaust conduit 36 opening therefrom, and control valves 37 and 38 will regulate the flow distribution out of the system or back to the furnace 25. Valve 35 will, of course, be closed.

By providing the moisture removing device 33 and connecting it to the material reducing system in the manner described, it will be practical to operate the system at a desirable oxygen deficient level and, more importantly, under temperature level conditions at the separator 15 that will not cause the product released at the discharge 16 from the separator to reach the spontaneous combustiontemperature level. Furthermore, the device'33 permits the system herein described to accept a reasonable level of moisture content of the product admitted to the mill l and to extract the moisture at the means 33 on a continuous basis so that it will not be necessary to operate the system at such a high temperature to control the moisture that spontaneous combustion in the final product is a problem. Thus, the system is efficiently operated for the purpose described by the proper setting of the dampers 29A, 35 and 37 to force a sufficient quantity of the moisture laden inert gases through the moisture extracting device 33 at a rate substantially equal to the rate of introduction at the reducing mill of moisture carried in by the freshly introduced raw material. It may be necessary, when exhausting some of the gaseous medium at conduit 36 to close valve 29A completely so the gaseous medium returned to the furnace 25 after being separated from its moisture can be regulated as desired and still supply any excess at conduit 36. ln either setting, the present system will permit the apparatus to operate while grinding or classifying material that might catch fire due to spontaneous combustion, and it performs this improved function by operating below the product spontaneous combustion temperature level without loosing its operating efficiency due to moisture accumulation in the system.

What is claimed is:

1. ln apparatus for reducing moisture containing raw material to a final product having, a raw material reducing mill, a separator, means connecting said mill and separator in a closed circuit in which the gaseous medium carries the mill output of material to the separator for separation from the gaseous medium, a source of oxygen deficient hot gaseous medium connected into said closed circuit, and a recirculation circuit connected between a portion of said closed circuit and said hot gas source; the improvement comprising: means in said recirculation. circuit to extract moisture from the gaseous medium flowing therethrough to said source of hot gaseous medium, whereby said source of hot gaseous medium returns the dried medium to said closed circuit.

2. The apparatus improvement of claim 1 including means to regulate the volume of medium subjected to said moisture extracting means.

3. The apparatus improvement of claim 1 including means in said recirculating circuit to exhaust to atmosphere a portion of the medium in said recirculating circuit, and means supplying primary ambient air to said source of hot gaseous medium in a volume to make up the volume exhausted to atmosphere.

4. In apparatus for reducing a raw material to a final product having a raw material reducing means, a first conduit system connected in series with said reducing means, a blower for forcing a flow of medium through said reducing means to carry the final product out of said reducing means, a separator device connected into said conduit system at a station to extract the final product from the flowing medium; a furnace connected into said conduit system system to supply oxygen deficient hot medium into said system, and a second conduit system connected between said first conduit system downstream of said blower and said furnace, the improvement comprising: moisture extracting means connected into said second conduit system to remove moisture from the flowing medium in advance of said furnace, a source of primary combustion air connected to said furnace, and means in said second conduit system to exhaust to atmosphere a portion of the medium flowing in said second conduit system.

5. In apparatus for reducing raw material to a final product having material size reducing means, a first gaseous medium conduit system connected in series with said reducing means, a blower connected into said first conduit system to force flow of the gaseous medium through said reducing means, a furnace connected into said conduit system in advance of said reducing means to supply hot oxygen deficient gaseous medi- 1 um into said first conduit system, the improvement comprising: a second conduit system connected between said first conduit system in advance of said reducing means and said furnace to recirculate at least a portion of the gaseous medium in said first conduit system through said furnace and means in said second conduit system to remove moisture from the recirculated gaseous medium in advance of said furnace.

6. The apparatus improvement of claim 5 wherein said second conduit system includes an outlet between said moisture removing means and said furnace to exhaust at least a portion of the dry oxygen deficient medium. 

1. In apparatus for reducing moisture containing raw material to a final product having, a raw material reducing mill, a separator, means connecting said mill and separator in a closed circuit in which the gaseous medium carries the mill output of material to the separator for separation from the gaseous medium, a source of oxygen deficient hot gaseous medium connected into said closed circuit, and a recirculation circuit connected between a portion of said closed circuit and said hot gas source; the improvement comprising: means in said recirculation circuit to extract moisture from the gaseous medium flowing therethrough to said source of hot gaseous medium, whereby said source of hot gaseous medium returns the dried medium to said closed circuit.
 2. The apparatus improvement of claim 1 including means to regulate the volume of medium subjected to said moisture extracting means.
 3. The apparatus improvement of claim 1 including means in said recirculating circuit to exhaust to atmosphere a portion of the medium in said recirculating circuit, and means supplying primary ambient air to said source of hot gaseous medium in a volume to make up the volume exhausted to atmosphere.
 4. In apparatus for reducing a raw material to a final product having a raw material reducing means, a first conduit system connected in series with said reducing means, a blower for forcing a flow of medium through said reducing means to carry the final product out of said reducing means, a separator device connected into said conduit system at a station to extract the final product from the flowing medium; a furnace connected into said conduit system system to supply oxygen deficient hot medium into said system, and a second conduit system connected between said first conduit system downstream of said blower and said furnace, the improvement comprising: moisture extracting means connected into said second conduit system to remove moisture from the flowing medium in advance of said furnace, a source of primary combustion air connected to said furnace, and means in said second conduit system to exhaust to atmosphere a portion of the medium flowing in said second conduit system.
 5. In apparatus for reducing raw material to a final product having material size reducing means, a first gaseous medium conduit system connected in series with said reducing means, a blower connected into said first conduit system to force flow of the gaseous medium through said reducing means, a furnace connected into said conduit system in advance of said reducing means to supply hot oxygen deficient gaseous medium into said first conduit system, the improvement comprising: a second conduit system connected between said first conduit system in advance of said reducing means and said furnace to recirculate at least a portion of the gaseous medium in said first conduit system through said furnace, and means in said second conduit system to remove moisture from the recirculated gaseous medium in advance of said furnace.
 6. The apparatus improvement of claim 5 wherein said second conduit system includes an outlet between said moisture removing means and said furnace to exhaust at least a portion of the dry oxygen deficient medium. 